Patent GB-674821-A (GB)
Title: Automatic pilot
IPC: G05D1/08
Filed: 1945-06-09
Abstract: 674,821. Automatic control systems for aircraft. BENDIX AVIATION CORPORATION. June 9, 1945 [May 29, 1944], No. 14665/45. Class 38 (iv). In an automatic pilot a three degree - of - freedom gyroscope supports a signal generator device which produces signals in response to deviation of the craft about the three axes. The Figure shows an arrangement in which displacement signals for controlling the craft are produced by the unit 10 which comprises an induction compass 11 of the type described in Specification 592,394, [Group XXXVI], providing azimuth signals stabilized by a 3 degrees of freedom gyro 30 which has Selsyns 31 and 32 providing roll and pitch signals coupled between appropriate gimbals. In the azimuth (rudder) control circuits, compass signals are applied to the stator of Selsyn 25 whose rotor 38 applies a signal to motor 44 through amplifier-frequency divider 41 when the craft heading deviates so that heading indicator 52, repeater transmitter 61, rotor 38 and rotor 62 of Selsyn 63 are all adjusted in accordance with the change. Rotor 62 is energized so that a signal is included in the rotor 67 of Selsyn 66 which is applied (assuming switches A and B are in the " 1 " or manual position) to amplifier 78 together with an opposing fraction of the signal from the stator of Selsyn 95 which is initially zero but increases as the amplifier output actuates motor 85, driving rod 73 which causes disc 70 to move off the centre of continuously rotating disc 74 so that rotor 67 and heading indicator 96 are driven towards correspondence with the compass until increasing signals from the stator of Selsyn 95 predominate whereupon motor 85 reverses until the signal from 67 predominates again. This " hunting " continues until the system returns to the initial position with the exception of rotor 67 which settles down in its new null position. When this has occurred, i.e. indicators 52 and 96 agree, switches A and B may be set to the automatic (2) position when any signals from stator 67 are fed to amplifier 97a which actuates rudder control motor 100 until positional feed-back signals from a Selsyn 109 cancels the amplifier input. To avoid hunting a rate of turn signal is fed from a gyroscopic rate of turn device 115 to the amplifier. Heading changes may be effected by rotating the stator of Selsyn 66 by means of knob 201, whereupon the craft makes a flat turn. Continuous turns are effected by displacing the stator of Selsyn 95 by knob 202, so that motor 85 drives the rotor of the Selsyn into a new pull position by moving rod 73 and in so doing offcentres disc 70 on disc 74 so that the rotor of Selsyn 66 is continuously rotated. Movement of the rod also causes associated cams 134 and 143 to move the rotor of Selsyns 126 and 136 in the roll and pitch circuits (see below) so that the craft executes a suitably banked turn without adopting a head-down attitude. Considering the elevator and aileron control circuits, signals from devices 31 and 32 are applied through Selsyns 126 and 136 to amplifiers 128 and 138 which control the ailerons and elevators in the same way as the rudder amplifier. Rate of turn signals being provided by devices 179 and 180, changes in attitude may be effected by rotating the stators of devices 126 and 136 by means of knobs 169 and 170. To enable the transition from manual to automatic control to be smoothly effected indicators 167 and 168 are provided to indicate if the associated amplifier outputs are equal to the positional feed-back signals from the control surfaces. Electromagnetically-operated clutches 105, 157 and 158 are provided to enable the automatic pilot when the craft is under manual control. The transmitter 61 is of the type described in Specification 565,277, [Group XXXVIII]. All the Selsyn devices may be replaced by devices of this type. Also the three amplifiers may be replaced by a single amplifier as in Specification 662,831.